According to Remo in Shulchan Aruch Yorah De'ah a9:2 as referred in this OU article, people should wait 6 hours after eating hard cheese.
Let's say someone eats a type of cheese that is partially hard cheese & partially non hard cheese. (The mix was intentionally done, incidentally, for explicit purpose of selling it this way. Let's say the cheese is called "Parmerican" - parmesan (aged) + processed "American") Does the person need to wait 6 hours because he ate some hard cheese? How much hard cheese would require waiting 6 hours - does it follow the same concept of "batul beshishim" (less than 1/60) as with milk accidentally mixed into a meat dish (i.e., less than 1/60 is nullified)? Is the amount based on majority (more than 50% hard cheese in the mix means 6 hours) or is there some other measurement in this mix that requires a 6-hour wait?